This invention relates to a window-pane cleaning device for cleaning window panes by using a squeezee and a method for controlling the same. The invention is directed to improving the cleaning efficiency drastically by employing a feedback control for controlling the squeezee in the pressing force applied thereto with two systems of servo devices.
As taller buildings are constructed, the number of windows provided in these buildings increases with accompanying necessity for regularly cleaning window-panes of these windows.
There has been a cleaning method currently in practice for cleaning window-panes according to which an operator in a moving scaffold hung from a roof of a building applies water on window-panes and wipes off water from the window-panes with a manually operated squeezee. This conventional cleaning method is inefficient and moreover is dangerous to the operator.
There has been developed a device for automatically cleaning window-panes. For example, as shown in FIG. 4, there is provided a cleaning unit 1 which is hung from a roof is capable of moving vertically. A squeezee 2 is mounted on this unit 1 such that the squeezee 2 abuts against a window-pane W and the fixing position of the squeezee 2 can be changed. Water is sprayed from a water spray nozzle 1 over the window-pane W and dust is wiped off with the squeezee 2 while the cleaning unit 1 is moved down. Soiled water is recovered and collected in a soiled water tank.
In such prior art window-pane cleaning device, it is necessary to press the squeezee 2 against the window-pane W with a constant force for effecting a satisfactory cleaning work without leaving an unwiped portion on the window-panes.
For this purpose, in the prior art cleaning device, the amount of projection of the squeezee 2 from the cleaning unit 1 is adjusted by changing the fixing position of the squeezee 2 before starting the cleaning work by moving down the cleaning unit 1.
Although the cleaning unit 1 of the prior art device is moved down along guides attached to the sides of each window of a building, there are irregularities in the mounting position of the guides and also mounting position of window-panes in each window due to errors in mounting these guides and window-panes. For this reason, the interval between the surface of the window-pane W and the cleaning unit 1 actually is not constant with resulting variation in the pressing force of the squeezee 2.
Hence, the squeezee 2 tends to be undesirably spaced away from the window-pane W as shown in FIG. 5b as compared to an optimum position shown in FIG. 5a or, conversely, approaches too close to the window-pane W as shown in FIG. 5c with resulting occurrence of unwiped portions on the window-panes W or increase in resistance to wiping by the squeezee 2 or leaving of scratches on the window-panes W.
Moreover, in a case where window-panes W continue horizontally and the cleaning operation must be made by moving the cleaning unit 1 in a horizontal direction, there are not only the above described error in mounting window-panes on windows but also a problem caused by a a window-pane with curved surface as shown in FIG. 5d provided in the corner portion of the building. In such curved portion of the window-pane, the distance between the surface of the window-pane W and the squeezee 2 varies inevitably with a result that an unwiped portion is left or, conversely, resistance in wiping increases.
In an attempt to overcome these problems, there has also been developed a cleaning device in which the amount of projection of the squeezee is adusted by stretching or withdrawing of arms of air cylinders. An expriment made with this cleaning device has made it clear that, as shown in FIGS. 6a and 6b, the pressing force of the squeezee in some case varies widely by a slight change in the amount of projection of the squeezee but in other case does not vary much despite a large change in the amount of projection of the squeezee, depending upon the state of contact of the squeezee against the surface of the window-pane. Thus, the relation between the pressing force of the squeezee and the amount of projection of the squeezee is not linear and, accordingly, the control system for adjusting the amount of projection of the squeezee by stretching or withdrawing air cylinders cannot improve the cleaning efficiency as expected.
It is, therefore, an object of the invention to provide a window-pane cleaning device and a method for controlling the same capable of cleaning window-panes by pressing a squeezee with a constant pressing force over the entire width of the window-pane notwithstanding variation in the distance between the squeezee and the window-pane whereby the cleaning efficiency can be remarkably improved.
It is another object of the invention to provide a method for controlling a window-pane cleaning device capable of controlling the squeezee always in an optimum condition during each period of starting cleaning, continuous cleaning and finishing cleaning.